This application is related to U.S. Pat. Nos. 7,422,693 and 7,327,443, which are hereby incorporated by reference in their entirety to the extent not inconsistent with the disclosure herein.
Blood collection and processing play important roles in the worldwide health care system. In conventional blood collection, blood is removed from a donor or patient, separated into its various blood components via centrifugation, filtration and/or elutriation and stored in sterile containers for future infusion into a patient for therapeutic use. Apheresis blood collection techniques have also been adopted in many blood collection centers wherein a selected component of blood is collected and the balance of the blood is returned to the donor during collection. An advantage of this method is that it allows more frequent donation from an individual donor because only a selected blood component is collected and purified.
Apheresis blood processing also plays an important role in a large number of therapeutic procedures. In these methods, blood is withdrawn from a patient undergoing therapy, separated, and a selected fraction is collected while the remainder is returned to the patient. For example, a patient may undergo leukapheresis prior to radiation therapy, whereby the white blood cell component of his blood is separated, collected and stored to avoid exposure to radiation. Further, apheresis may be used to perform therapeutic platelet depletion for patients having thrombocytosis and therapeutic plasma exchange for patients with autoimmune diseases.
Both conventional blood collection and apheresis systems typically employ differential centrifugation methods for separating blood into its various blood components. In differential centrifugation, blood is circulated through a sterile separation chamber, which is rotated at high rotational speeds about a central rotation axis. The centrifugal force generated upon rotation separates particles suspended in the blood sample into discrete fractions having different densities. Descriptions of blood centrifugation devices are provided in U.S. Pat. No. 5,653,887 and U.S. Pat. No. 7,033,512.
To achieve continuous, high throughput blood separation, extraction or collection ports are provided in most separation chambers. Extraction ports are disposed at selected positions along the separation axis corresponding to discrete blood components. To ensure the extracted fluid exiting a selected extraction port is substantially limited to a single phase, however, the phase boundaries between the separated blood components must be positioned along the separation axis such that an extraction port contacts a single phase, such as platelet enriched plasma, white blood cells, or red blood cells.
The purity of extracted blood components using density centrifugation is currently limited by the control of the position of phase boundary layers between separated components. Given the sensitivity of the phase boundary position to many variables, which change from person to person and during processing, it is important to monitor the position of the phase boundaries during blood processing to ensure optimal separation conditions are maintained and the desired purity of selected blood components is achieved. In addition, accurate characterization of the positions of phase boundaries allows for separation conditions to be adjusted and optimized for changes in blood composition during processing.
It will be appreciated from the foregoing that a need exists for methods and devices for monitoring and controlling the processing of whole blood samples and blood component samples. Particularly, optical monitoring methods and devices are needed which are capable of accurately characterizing the separation, extraction and collection of blood components processed by density centrifugation, including providing controlled stroboscopic light sources with consistent duration and intensity of illumination.